JPS6287317A - Injection control of injection molder - Google Patents

Abstract

PURPOSE:To stabilize the flow of molten resin and consequently smoothly mold good quality product by a method wherein the deviation between pressures, which are measured with pressure detectors provided at two positions on the downstream side of a back-flow prevention valve when a screw advances to its limit, is controlled to be constant. CONSTITUTION:A transducer 11 converts a pressure P1 detected with a pressure sensor 7 and a pressure P2 detected with a pressure sensor 8 into voltages. A calculating part 12 calculates P2-P1 by being inputted with the pressures P1 and P2 converted at the transducer 11 so as to send injection speed in a form of input signal to an injection pressure controlling part 13, to which the reference value of the value of pressure difference set in advance at a setter 14 is inputted, in order to closed-loop-control a servo valve or solenoid proportioning valve 15 for injection. In order to keep the injection speed and injection pressure constant, if the pressure P2 rises, the pressure P1 rises in order to keep the pressure difference constant. If the pressure P2 lowers, the pressure P1 lowers in order to keep the pressure difference constant. As a result, the flow or the resin is stabilized at al times and smooth molding can be performed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an injection control method for controlling injection speed or injection pressure in a filling process of an injection molding machine.

<Prior Art and Its Disadvantages> In conventional programmable injection molding machines, setting the injection speed and injection pressure to suit individual molds and resin materials requires experience and skill, and is extremely troublesome.

<Object of the Invention> The present invention eliminates the above-mentioned drawbacks, simplifies the setting conditions for molding, and makes it possible to mold good products.

<Summary of the Invention> In order to achieve the above-mentioned object, pressure detectors are disposed at two positions downstream of the check valve at the time when the screw advance of the heating cylinder of the injection molding machine is limited, and the two pressure detectors detect the pressure. The present invention provides an injection control method for an injection molding machine, characterized in that speed control or pressure control of an injection filling process is performed based on pressure deviation.

Alternatively, one of the two pressure detectors may be
This is an injection control method for an injection molding machine, characterized in that the pressure detector is provided in the mold, and as another method, one of the two pressure detectors is provided in a part of the sprue. This is an injection control method for an injection molding machine.

<Example> Next, one example of the present invention will be described with reference to FIG. Reference numeral 1 denotes a heating cylinder of an injection molding machine, and a block IJ:L2 is fitted onto the inner diameter surface of the cylinder, and is moved forward and backward in the axial direction by a drive device (not shown) and is driven to rotate around the shaft. The screw 2 transfers the material resin supplied from a hopper (not shown) to the front of the screw head 3, and after accumulating a certain amount in the cavity 4 in front of the screw head 3 (the screw itself moves to the retracted position). ), the material resin accumulated in the cavity 4 is injected into the mold cavity 5. (Position shown in the figure) At this time, a check valve 6 is attached to the scree 2 to direct the material resin to the hopper side (to the right in the figure).

Reference numeral 7 denotes a pressure sensor provided on the downstream (left side in the figure) side of the check valve 6 when the screw 2 is at the forward limit position. 8
is a second pressure sensor provided further downstream than the pressure sensor. A sprue 9 connects the mold cavity 5 and the nozzle hole 10 at the tip of the heating cylinder 1. A converter 11 converts the pressure P detected by the pressure sensor 7 and the pressure P2 detected by the second pressure sensor 8 into voltage. 12 is an arithmetic unit which represents the pressure P converted by the converter 11;
l and P2 are input, P2-Pl is calculated, and the injection speed is sent to the injection pressure control section 13 as an input signal. At this time, a pressure difference value previously set in the setting device 14 is inputted as a reference value to the control section 13, and the servo valve or electromagnetic proportional valve 15 for injection is controlled in a closed loop.

<Effects> Since the structure is as described above, in order to keep the injection speed and injection pressure constant, if the pressure of P2 increases,
To keep the pressure difference constant, the pressure of Pl increases, and when the pressure of P2 decreases, Pl also decreases to keep the pressure difference constant.
The flow of the resin is always stable and smoother molding can be easily performed.

Also, as shown in FIG. 2, a second pressure sensor 8a.

8b may be provided in the mold cavity 5 or the sprue 9.

As explained above, the molding conditions can be easily set by controlling the pressure deviation to be constant using the pressure detectors installed at two positions downstream of the check valve at the screw advance limit, and the flow of the molten resin. It is also stable and allows smooth molding of good products.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the invention, and FIG. 2 is a diagram showing another embodiment of the invention.

Claims (1)

[Scope of Claims] 1. Pressure detectors are disposed at two positions downstream of the check valve at the time when the screw advance of the heating cylinder of the injection molding machine is limited, and injection is detected by the deviation of the pressure detected by the two pressure detectors. An injection control method for an injection molding machine, characterized by controlling the speed or pressure of a filling process. 2. The injection control method for an injection molding machine according to claim 1, wherein one of the pressure detectors is provided within the mold. 3. The injection control method for an injection molding machine according to claim 1, wherein one of the pressure detectors is provided in a spool portion.